CVE-2019-15226

CVE-2019-15226 is a high-severity vulnerability in Envoyproxy Envoy with a CVSS 3.x base score of 7.5. Its EPSS exploit-prediction score of 65% places it in the 99th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-400.

Key facts

Description

Upon receiving each incoming request header data, Envoy will iterate over existing request headers to verify that the total size of the headers stays below a maximum limit. The implementation in versions 1.10.0 through 1.11.1 for HTTP/1.x traffic and all versions of Envoy for HTTP/2 traffic had O(n^2) performance characteristics. A remote attacker may craft a request that stays below the maximum request header size but consists of many thousands of small headers to consume CPU and result in a denial-of-service attack.

Frequently asked questions

What is CVE-2019-15226?
Upon receiving each incoming request header data, Envoy will iterate over existing request headers to verify that the total size of the headers stays below a maximum limit. The implementation in versions 1.10.0 through 1.11.1 for HTTP/1.x traffic and all versions of Envoy for HTTP/2 traffic had O(n^2) performance characteristics. A remote attacker may craft a request that stays below the maximum request header size but consists of many thousands of small headers to consume CPU and result in a denial-of-service attack.
How severe is CVE-2019-15226?
CVE-2019-15226 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2019-15226 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 65% (99th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2019-15226?
CVE-2019-15226 primarily affects Envoyproxy Envoy. In total, 16 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2019-15226?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2019-15226 published?
CVE-2019-15226 was published on 2019-10-09 and last updated on 2026-06-17.

References

Affected products (16)

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